Private branch exchange (PBX) and automated call distributors provide enterprises with digital voice service and centralized connectivity to the public switched telephone network (PSTN). Incoming telephone calls are routed to specific agents through the PBX or call distributor. Agents local to the PBX are connected to the PBX via subscriber equipment such as a telephone.
The call distributor or PBX may support packet-based voice communications for local subscriber equipment. The use of packet based voice communications typically enables the enterprise to integrate voice and data communications over the same physical network. Moreover, the use of packet based voice communications enables inexpensive communication with agents that may be geographically distant from the PBX.
For small geographic areas, a packet based network can offer acceptable quality of service for voice communications. Unfortunately, packets are subject to noticeable delay and loss over larger geographic distances. These delays and losses tend to result in unacceptable quality of service for voice communications over larger geographic areas.